Novel products and processes

ABSTRACT

Novel photographic products for use in diffusion transfer systems for forming visible images, particularly systems for forming color images viewable, without separation as color reflection prints, which products include a neutralizing layer for lowering the environmental pH after application of an aqueous alkaline processing fluid, the neutralizing layer comprising a water-soluble acidic compound and a hydrophobic reagent obtained from a water-soluble precursor contained in the aqueous coating solution employed to prepare the neutralizing layer.

United States Patent 1191 m1 3,819,371 June 25, 1974 Sahatjian et al.

[ NOVEL PRODUCTS AND PROCESSES [75] Inventors: Ronald A. Sahatjian, Watertown;

Lloyd D. Taylor, Lexington, both of Mass.

[73] Assignee: Polaroid Corporation, Cambridge,

Mass.

[22 Filed: Mar.6, 1972 21 Appl. No.: 231,835

[52] US. Cl. 96/3, 96/29 D, 96/77,

, 117/161 LN I [51] Int. Cl. G03c 7/00, G030 5/54, G03c 1/40 [58] Field of Search 96/29 D, 77, 3; I 1 117/161 LN 56] References Cited UNITED STATES PATENTS 2,280,986 4/1942 Toland et al. 117/161 LN I 3,090,762 1 5/1963 Maeder et al. 117/161 LN 3,415,645 Land 96/3 3,482,972 12/1969 ldelson 96/29 D 3,674,478 7/1972 Grasshoff et a1 96/29 D 3,705,184 12/1972 Goulston et al. 96/29 D Primary ExamineF-Norman G. Torchin Assistant Examiner-Richard L. Schilling [5 7] ABSTRACT Novel photographic products for use in diffusion transfer systems for forming visible images, particularly systems for forming color images viewable, without separation as color reflection prints, which products include a neutralizing layer for lowering the environmental pl-l after application of an aqueous alkaline processing fluid, the neutralizing layer comprising a water-soluble acidic compound and a hydrophobic reagent obtained from a water-soluble precursor contained in the aqueous coating solution employed to prepare the neutralizing layer.

23 Claims, 1 Drawing Figure DYE DEVELOPER LAYER RED-SENSITIVE SlLVER HALIDE EMULSION LAYER .DYE DEVELOPER LAYER SILVER llALIDE YER 0v: DEVELOPER LAYER SILVER HALIDE LAYER RECEIVING LAYER LAYER NEUTRALIZING LAYER PPORT' PAIENIEBmesmm CYAN DYE DEVELOPER LAYER REDSENSITIV LVER HALIDE EMULSION LAY INTERLAYER /Ii MAGENTA DYE DEVELOPER LAYER GREEN- NSITIVE SILVER HALIDE EMULS LAYER f'NTER LAYER I YELLOW DYE DEVELOPER LAYER BLUE-SENSITIVE SILVER HALIDE EMULSION LAYER /IMAGE- RECEIVING LAYER I/SPACER LAYER k- N EUTRALIZING LAYER SUPPORT NOVEL PRODUCTS AND PROCESSES BACKGROUND OF THE INVENTION Various diffusion transfer systems for forming color images have heretofore been disclosed in the art. Generally speaking, such systems rely for color image formation upon a differential in mobility or solubility of a dye image-providing material obtained as a function of development so as to provide an imagewise distribution of such material which is more diffusible and which is therefore selectively transferred, at least in part, by diffusion, to a superposed dyeable stratum to impart thereto the desired color transfer image. The differential in mobility or solubility may for example be obtained by a chemical action such as a redox reaction or a coupling reaction.

The dye image-providing materials which may be employed in such processes generally may be characterized as either (I) initially soluble or diffusible in the processing composition but are selectively rendered nondiffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-diffusible in the processing composition but which are selectively rendered diffusible in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.

As examples of initially soluble or diffusible materials and their application in color diffusion transfer, mention may be made of those disclosed, for example, in US. Pat. Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 2,774,668; and 2,983,606. As examples of initially non-diffusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in U.S. Pat. Nos. 3,443,939; 3,443,940; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294 and 3,445,228.

In any of these systems, multicolor images are obtained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith a dye image-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the so-called tripack structures employing a blue-, a greenand a red-sensitive silver halide layer having associated therewith, respectively, a yellow, a magenta and a cyan dye image-providing material.

A particularly useful system for forming color images by diffusion transfer is that described in US. Pat. No. 2,983,606, employing dye developers (dyes which are also silver halide developing agents) as the dye imageproviding materials. In such systems, a photosensitive element comprising at least one silver halide layer having a dye developer associated therewith (in the same or in an adjacent layer) is developed by applying an aqueous alkaline processing composition. Exposed and developable silver halide is developed by the dye developer which in turn becomes oxidized to provide an oxidation product which is appreciably less diffusible than the unreacted dye developer, thereby providing an imagewise distribution of diffusible dye developer in terms of unexposed areas of the silver halide layer, which imagewise distribution is then transferred, at least in part, by diffusion, to a dyeable stratum to impart thereto a positive dye transfer image. Multicolor images may be obtained with a photosensitive element having two or more selectively sensitized silver halide layers and associated dye developers, a tripack structure of the type described above and in various patents including the aforementioned US. Pat. No. 2,983,606 being especially suitable for accurate color recordation of the original subject matter.

In color diffusion transfer systems of the foregoing description, color images are obtained by exposing a photosensitive element or negative component comprising at least a light-sensitive layer, e. g., a gelatino silver halide emulsion layer, having a dye imageproviding material associated therewith in the same or in an adjacent layer, to form a developable image; developing this exposed element with a processing composition to form an imagewise distribution of a soluble and diffusible image-providing material; and transferring this imagewise distribution, at least in part, by diffusion, to a superposed receiving element or positive component comprising at least a dyeable stratum to impart to this stratum a color transfer image. The negative and positive components may be separate elements which are brought together during processing and therafter either retained together as the final print or separated following image formation; or they may together comprise a unitary structure, e.g., integral negativepositive film units wherein the negative and positive components are laminated and/or otherwise physically retained together at least prior to image formation.

While the present invention is applicable both to those systems wherein the dyeable stratum is contained on a separate element and to those systems wherein the dyeable-stratum and the photosensitive strata comprise a unitary structure, of particular interest are those integral negative-positive film units adapted for forming color transfer images viewable without separation, i.e., wherein the positive component need not be separated from the negative component for viewing purposes. Generally, such film units comprise a plurality of essential layers including a negative component comprising at least one light-sensitive silver halide and associated dye image-providing material and a positive component comprising dyeable stratum. These components may be laminated together or otherwise secured together in physical juxtaposition as-a single structure. Film units intended to provide multicolor images comprise two or more selectively sensitized silver halide layers each having associated therewith an appropriate dye image-providing material exhibiting desired spectral absorption characteristics. As was heretofore mentioned the most commonly employed negative components for forming multicolor images are of the tripack structure containing a blue-, a greenand a redsensitive silver halide layer having associated therewith in the same or in a contiguous layer a yellow, a magenta and a cyan dye image-providing material respectively. lnterlayers or spacer layers may if desired be provided between the respective silver halide layers and asso ciated dye image-providing materials. In addition to the aforementioned essential layers, such film units further include means for providing a reflecting layer between the dyeable stratum and the negative component in order to mask effectively the silver image or images formed as a function of development of the silver hal ide layer or layers and any remaining associated dye image-providing material and to provide a background for viewing the color image formed in the dyeable stratum, without separation, by reflected light. This reflecting layer may comprise a preformed layer of a reflecting agent included in the essential layers of the film unit or the reflecting agent may be provided after photoexposure, e.g., by including the reflecting agent in the processing composition. These essential layers are preferably contained on a transparent dimensionally stable layer or support member positioned closest to the dyeable stratum so that the resulting transfer image is viewable through this transparent layer. Most preferably another dimensionally stable layer which may be transparent or opaque is positioned on the opposed surface of the essential layers so that the aforementioned essential layers are sandwiched or confined between a pair of dimensionally stable layers or support members, at least one of each is transparent to permit viewing therethrough of a color transfer image obtained as a function of development of the exposed film unit in accordance with the known color diffusion transfer system such as will be detailed hereinafter. In a particularly preferred form such film units are employed in conjunction with a rupturable container of known description containing the requisite processing composition and adapted upon application of pressure of applying its contents to develop the exposed film unit, e.g., by applying the processing composition in a substantially uniform layer between the dyeable stratum and the negative component. It will be appreciated that the film unit may optionally contain other layers performing specific desired functions, e.g., spacer layers, etc.

Opacifying means may be provided on either side of the negative component so that the film unit may be processed in the light to provide the desired color transfer image. In a particularly useful embodiment such opacifying means comprise an opaque dimensionally stable layer or support member positioned on the free or outer surface of the negative component, i.e., on the surface of the film unit opposed from the positive component containing the dyeable stratum to prevent photoexposure by actinic light incident thereon from this side of the film unit and an opacifying agent applied during development between the dyeable stratum and the negative component, e.g., by including the opacifying agent in a developing composition so applied, in order to prevent further exposure (fogging) by actinic light incident thereof from the other side of the film unit when the thus exposed film unit is developed in the light. The last-mentioned opacifying agent may comprise the aforementioned reflecting agent which masks the negative component and provides the requisite background for viewing the transfer image formed thereover. Where this reflecting agent does not by itself provide the requisite opacity it may be employed in combination with an additional opacifying agent in order to prevent further exposure of the lightsensitive silver halide layer or layers by actinic light incident thereon.

As examples of such integral negative-positive film units for preparing color transfer image viewable without separation as reflection prints, mention may be made of those described and claimed in U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646; 3,473,925; 3,573,043; 3,576,625; 3,573,042; 3,594,164; and 3,594,165.

In general, the integral negative-positive film units of the foregoing description, e.g., those described in the aforementioned patents, are exposed to form a developable image and thereafter developed by applying the appropriate processing composition to develop exposed silver halide and to form, as a function of development, an imagewise distribution of diffusible dye image-providing material which is transferred, at least in part by diffusion, to the dyeable stratum to impart thereto the desired color transfer image, e. g., a positive color transfer image. Common to all of these systems is the provision of a reflecting layer between the dyeable stratum and the photosensitive strata to mask effectively the latter and to provide a background for viewing the color image contained in the dyeable stratum, whereby this image is viewable without separation, from the other layers or elements of the film unit. In certain of these systems, this reflecting layer is provided prior to photoexposure, e. g., as a preformed layer included in the essential layers of the laminar structure comprising the film unit, and in others it is provided at some time thereafter, e.g., by including a suitable lightreflecting agent, for example, a white pigment such as titanium dioxide, in the processing composition which is applied between the dyeable stratum and the next adjacent layer to develop the latent image and to form the color transfer image.

The dye image-providing materials which may be employed in such processes generally are selected from those materials heretofore mentioned and disclosed in the illustrative patents which were initially soluble or diffusible in the processing composition but which are selectively rendered non-diffusible as a function of development or those which are initially insoluble or nondiffusible in the processing composition but are selectively rendered diffusible as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.

A preferred opacification system to be contained in the processing composition is that described in the copending applications of Edwin 11. Land, Ser. No. 43,782, filed June 5, 1970 and now abandoned, and Ser. No. 101,968, filed Dec. 28, 1970 and now U.S. Pat. No. 3,647,437, comprising an inorganic reflecting pigment dispersion containing at least one optical filter agent at a pH above the pKa of the optical filter agent in a concentration effective, when the processing composition is applied, to provide a layer exhibiting optical transmission density than about 6.0 density units with respect to incident radiation actinic to the photosensitive silver halide layer and optical reflection density than about 1.0 density with respect to incident visible radiation.

In lieu of having the reflecting pigment contained in the processing composition, e.g., as disclosed in the aforementioned copending applications, the reflecting pigment needed to mask the photosensitive strata and to provide the requisite background for viewing the color transfer image formed in the receiving layer may be contained initially in whole or in part as a preformed layer in the film unit. As an example of such a preformed layer, mention may be made of that disclosed on the copending applications of Edwin H. Land, Ser. Nos. 846,441, filed July 31, 1969, now U.S. Pat. No. 3,615,421 and 3,645, filed Jan. 19,1970 and now U.S. Pat. No. 3,620,724. The reflecting pigment may be generated in situ as is disclosed in the copending applications of Edwin H. Land, Ser. Nos. 43,741 and 43,742, both filed June 5, 1970 and now U.S. Pat. Nos. 3,647,434 and 3,647,435, respectively.

in the various color diffusion transfer systems which have previously been described and which employ an aqueous alkaline processing fluid, it is well known to employ an acid-containing layer to lower the environmental pH following substantial dye transfer in order to increase the image stability and/or to adjust the pH from a first pH at which the imaging dyes are diffusible to a second (lower) pH at which they are not. For example, U.S. Pat. No. 3,362,819 discloses systems wherein the desired pH reduction may be effected by providing a polymeric acid layeradjacent the dyeable stratum. These polymeric acids may be polymers which contain acid groups, e.g., carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals or with organic bases; or potentially acidyielding groups such as anhydrides or lactones. Preferably the acid polymer contains free carboxyl groups. An inert interlayer or spacer layer may be disposed between the polymeric acid layer and the dyeable stratum in order to control the pH reduction so that it is not premature and hence interferes with the development process, e.g., to time control the pH reduction. Suitable spacer or timer" layers for this purpose are described with particularity in this patent and in others, including US. Pat. Nos. 3,419,389; 3,421,893; 3,433,633; 3,455,686; and 3,575,701.

The copending application of'schlein et al., Ser. No. 165,171, filed July 22, 1971, now US. Pat. No. 3,756,815, describes and claims an acid layer comprising a water-soluble acid and a water-soluble binder in film units such as those previously described and including a negative component comprising at least one light-sensitive silver halide layer and an associated dye image-providing material and a positive component containing a dyeable stratum. As is disclosed in this copending application, the use of such water-soluble ingredients in the neutralizing layer affords many distinct advantages over systems employing water-insoluble components which need be coated from an organic solvent. Apart from the readily apparent coating advantages in avoiding the use of organic solvents, is that it permits the use of shorter acid molecules with lower equivalent weights, which in turn permits one to employ thinner coatings, an important advantage in the film units to which the copending application is directed.

The copending application of Stanley F. Bedell, Ser. No. 214,746, filed Jan. 3, 1972, relates to another system for preparing neutralizing layers from aqueous mediums, these neutralizing layers comprising a graft copolymer of an acid moiety grafted onto a backbone. As is disclosed in this copending application, such graft polymers provide a neutralizing layer which is characterized asbeing hydrophobic and possessing an extremely high peal force so as to be extremely adherent against separation or delamination from the contiguous layers of the photograhic product in which it is employed. 1

While the acid layer is preferably contained in the receiving element employed in systems wherein the dye- The present invention is directed to another type of neutralizing material for lowering the environmental pH in color diffusion transfer systems of the type previously described, which material provides the distinct advantages and beneficial results which will be described hereinafter in the detailed description of the invention.

SUMMARY OF THE INVENTION In accordance with'the present invention, the neutralizing layer is prepared by applying an aqueous solution including a water-soluble acidic compound and a water-soluble precursor which at some time subsequent to coating may be treated to provide a hydrophobic reagent which provides to the thus coated layer wet strength and adhesion not possessed by the watersoluble acidic compound alone so as to provide a neutralizing layer which, apart from having the advantages of being coated from an aqueous solution, also possesses acceptable adhesion against delamination from the contiguous layers in the photographic product.

BRIEF DESCRIPTION OF DRAWING The FIGURE is an enlarged, fragmentary, diagramatic, sectional view of a film unit contemplated by this invention.

DESCRIPTION OF PREFERRED EMBODIMENT The preferred water-soluble precursors for forming the hydrophobic reagent are prepolymers which, upon subsequent treatment, e.g., condensation polymerization reaction conditions, form the hydrophobic reagent. The preferred photographic products employing the neutralizing layers of this invention are of the socalled integral negative-positive tripack configuration, the positive component of these film units including the neutralizing layer in addition to the dyeable stratum. Most preferably a timing or spacer layer of known description is disposed between the dyeable stratum and neutralizing layer, the preferred such timing layer being a polyvinylamide graft copolymer of the type described and claimed in US. Pat. No. 3,575,701 of Lloyd D. Taylor.

As was heretofore mentioned, the present invention is directed to neutralizing layers performing their known function in photographic systems such as were previously described, which neutralizing layers can be prepared from aqueous coating solutions. More specifically, the primary objectives of the invention are to achieve the advantages inherent in the use of such aqueous coating techniques while at the same time obviating certain disadvantages which are in general found in the employment of hydrophilic acidic compounds. The manufacturing advantages in employing aqueous coatings instead of organic solvents are obvious. Chief of these advantages are the elimination of the need for organic solvents which are typically volatile, their storage before use, special equipment needed for coating and recovery or recycling, the inherent danger in the use of volatile solvents as well as the possible contamination of the neutralizing layer due to the presence of trace amounts of these chemicals.

On the other hand, employment of water-soluble or hydrophilic acidic compounds to provide the neutralizing layer from an aqueous solution presents certain inherent disadvantages in the final laminar product. With the use of such hydrophilic acids, there is the inherent problem of water from the processing fluid piling up at the neutralizing layer and/ or at the interface of the neutralizing layer and the timing layer. This piling up of water in turn causes certain distinct problems, chief of which is the tendency for delamination to occur, which separation renders the final print objectionable. While this problem is most pronounced in those film units wherein the negative and positive components are retained together so that the processing fluid remains confined therebetween, e.g., in the heretofore described integral film units, it is also a problem, although to a lesser extent, in those systems wherein the respective negative and positive components are retained on separate elements which are separated following image formation.

One solution to this problem is the graft polymers described and claimed in the aforementioned copending application of Stanley F. Bedell, Ser. No. 214,746.

In accordance with the present invention, the neutralizing layer of the photographic products in which it is employed is prepared by coating from an aqueous solution of a water-soluble acidic compound and a watersoluble precursor which upon after-treatment of the thus coated solution provides the layer comprising the aforementioned acidic compound and a hydrophobic reagent providing the wet strength and adhesion not possessed by the acidic compound alone so that the resulting neutralizing layer will have the requisite adhesion against delamination.

This reagent may be defined as being a hydrophobic adhesive"; and the precursor employed to obtain this reagent subsequent to coating may be referred to as a hydrophilic precursor for the hydrophobic adhesive.

As examples of water-soluble acidic compounds which may be employed in the coating solution to prepare the neutralizing layers of this invention, mention may be made of water-soluble acid such as carboxylic or sulfonic acids which are capable of forming salts with alkali metals such as sodium, potassium, etc., or with organic bases or potentially acid-yielding compounds such as anhydrides or lactones or compounds containing other groups which are capable of reacting with bases to capture and retain them. As examples of useful water-soluble acidic compounds, mention may be made of polymeric acids such as ethylene/maleic anhydride copolymers, poly(methyl vinyl ether/maleic anhydrides) such as those commercially available from General Aniline and Film Corporation under the tradenames Gantrez ANl l9, Gantrez AN-l39 or Gantrez AN-l69, water-soluble polyacrylic acids, polymethacrylic acids, copolymers of styrene and maleic acid, etc.

As examples of useful precursors which may be employed to obtain the hydrophogic adhesive, mention may be made of water-soluble prepolymers which, upon subsequent treatment, e.g., condensation polymerization reaction conditions, form this hydrophobic reagent. Preferred prepolymers of this description are the amino resin prepolymers, e.g., ureaformaldehyde prepolymers having at least one mole of urea which has reacted with at least two moles of formaldehyde. These prepolymers may also be referred to as being low molecular weight polymers which are water-soluble but which, upon curing after coating from an aqueous medium, form higher molecular weight polymers, i.e., condensation polymers which are characterized as hydrophobic. The chemistry by which such amino resins are prepared is known and accordingly per se comprises no part of this invention. In general, the hydrophobic resins are formed by the steps of l methylolation of the amino groups of the amino-bearing material with formaldehyde to form the prepolymer; (2) initiating resin formation in aqueous solution by hydrogen ions, e.g., a strong mineral acid such as hydrochloric acid or nitric acid to obtain a curable product; and (3) curing, preferably at elevated temperatures, to form the resin. While this reaction is per se old, it has never been suggested that such an amino resin may be incorporated in a neutralizing layer from an aqueous coating solution by coating on the aqueous curable product (precursor) and then curing to provide a layer containing the water-insoluble resin.

To further illustrate the practice of this invention, a neutralizing layer may be prepared by applying to the desired layer or sheet material an aqueous solution including a watersoluble acid such as ethylene/maleic anhydride copolymer, a urea-formaldehyde prepolymer such as those commercially available, e.g., dimethylolurea, available from Olin Mathieson Chemical Corporation or QR-492 from Rohm & Haas Company and an acid such as hydrochloric or nitric; and then curing by heating at elevated temperatures, e.g., by coating the aqueous solution at a rate of on the order of 12 ft./min. and then heating to about 230265F. While not necessary to do so, it has been found that the condensation polymerization reaction occurs more expeditiously if additional formaldehyde and/or some other water-soluble difunctional aldehyde, e.g., succindialdehyde, is included in the aqueous coating solution, for example, in amounts equal by weight to the prepolymers in this solution. The ratio of hydrophobic reagent to acidic compound in the resulting neutralizing layer may be on the order of from about 1:5 to about 1:20, a preferred ratio being on the order of about 10:1. The resulting neutralizing layer typically contains less than about 3,000 mgs. of solids per sq. ft. of surface area. The precise ratios and/or coverages may vary with a given film unit and photographic system, as will be appreciated by one skilled in the art, and the foregoing is only by way of illustration of a typical neutralizing layer of this invention. strata,

As was heretofore mentioned, the neutralizing layer of this invention is useful in systems wherein the photosensitive strata and the dyeable stratum are contained on separate elements; and in systems wherein they are contained together as a unitary film unit, e.g., in the integral negative-positive film units previously described. In the former type, the neutralizing layer is most preferably contained in association with the dyeable stratum, e.g., in an image-receiving element comprising a support carrying the neutralizing layer and the dyeable stratum, a spacer or timing layer preferably being disposed therebetween. It may however be contained as a layer in the photosensitive element, i.e., in the element containing the photosensitive strat, as is disclosed in U.S. Pat. No. 3,362,821. In like manner, in the integral negative-positive film units, the neutralizing layer is preferably associated with the dyeable stratum, e.g., on the side of the dyeable stratum opposed from the negative component, and most preferably a timing" layer is disposed between the neutralizing layer and dyeable stratum.

Of particular interest are those film units such as the heretofore described integral negative-positive film units wherein the negative and positive components are at least retained together after image formation as the final print. The invention will accordingly be illustrated by reference to a typical film unit of this description.

As shown in the drawing, such a film unit may comprise, as the essential layers, a layer 13 of cyan dye developer, red-sensitive silver halide emulsion layer 14, interlayer 15, a layer of magenta dye developer 16, a greensensitive silver halide emulsion layer 17, an interlayer 18, yellow dye developer layer 19, blue-sensitive silver halide emulsion layer 20, auxiliary layer 21, image receiving layer or dyeable stratum 22, spacer layer 23, and a pH-reducing or neutralizing layer 24. Layers 13-21 comprise the negative component and layers 22-24 comprise the positive component. These essential layers are shown to be confined between adimensionally stable layer or support member 12 which is preferably opaque so as to permit development in the light and dimensionally stable layer or support member 25 which is effectively transparent to permit viewing of a color transfer image formed as a function of development in receiving layer or dyeable stratum 22.

Layers l2 and 25 are preferably dimensionally stable liquid-impermeable layers which when taken together may possess a processing composition solvent vapor permeably sufficient to effect, subsequent to substantial transfer image formation and prior to any substantial environmental image degradation to which the re sulting image may be prone, osmotic transpiration of processing composition solvent in a quantity effective to decrease the solvent from a first concentration at which the color-providing material is diffusible to a second concentration at which it is not. Although these layers may. possess a vapor transmission rate of l or less gms/24 hrs./ 100 in. /mil., they preferably possess a vapor transmission .rate for the processing composition solvent averaging not less than about 100 gms./24 hrs/100 inf/mil, most preferably in terms of the preferred solvent, water, a vapor transmission rate averaging in excess of about 300 gms. of water/24 hrs./ 100 in. /mil., and may advantageously comprise a microporous polymeric film possessing a pore distribution which does not unduly interfere with the dimensional stability of the layers or, where required, the optical characteristics of such layers. As examples of useful materials of this nature, mention may be made of those having the aforementioned characteristics and which are derived from ethylene glycol terephthalic acid; vinyl chloride polymers; polyvinyl acetate; cellulose derivatives, etc. As heretofore noted layer 12 is of sufficient opacity to prevent fogging from occurring by light passing therethrough, and layer 26 is transparent to permit photoexposure and for viewing of a transfer image formed on receiving layer 23.

The silver halide layers preferably comprise photosensitive silver halide, e.g., silver chloride, bromide or iodide or mixed silver halides such as silver iodobromide or chloriodobromide dispersed in a suitable colloidal binder such as gelatin and such layers may typically be on the order of 0.6 to 6 microns in thickness. it will be appreciated that the silver halide layers may and in fact generally do contain other adjuncts, e.g., chemical sensitizers such as are disclosed in US. Pat. Nos. 1,574,944; 1,623,499; 2,410,689; 2,597,856; 2,597,915; 2,487,850; 2,518,698; 2,521,926; etc.; as well as other additives performing specific desired functions, e.g., coating aids, hardeners, viscosityincreasing agents, stabilizers, preservatives, ultraviolet absorbers and/or speed-increasing compounds. While the preferred binder for the silver halide is gelatin, others such as albuminfcasein, zein, resins such as cellulose derivatives, polyacrylamides, vinyl polymers, etc., may replace the gelatin in whole or in part.

The respective dye developers, which may be any of those heretofore known in the art and disclosed for example in US. Pat. No. 2,983,606, etc., are preferably dispersed in an aqueous alkaline permeable polymeric binder, e. g., gelatin as a layer from about 1 to 7 microns in thickness.

Interlayers l5, l8 and 21 may comprise an alkaline permeable polymeric material such as gelatin and may be on the order of from about 1 to 5 microns in thickness. As examples of other materials for forming these interlayers, mention may be made of those disclosed in US. Pat. Nos. 3,421,892, 3,575,701, 3,615,422 and 3,625,685. These interlayers, may also contain additional reagents performing specific functions and the various ingredients necessary for development may also be contained initially in such layers in lieu of being present initially in the processing composition, in which event the desired developing composition is obtained by contacting such layers with the solvent for forming the processing composition, which solvent may include the other necessary ingredients dissolved therein.

The image-receiving layer may be on the order of 0.25 to 0.4 mil. in thickness. Typical materials heretofore employed for this layer include dyeable polymers such as nylon, e.g., N-methoxymethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without plasticizers; cellulose acetate with filler as, for example, onehalf cellulose acetate and one-half oleic acid; gelatin; polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, etc. Such receiving layers may, if desired, contain suitable mordants, e.g., any of the conventional mordant materials for acid dyes such as those disclosed, for example, in the aforementioned US. Pat. No. 3,227,550; as well as other additives such as ultraviolet absorbers. pH-reducing substances, etc. It may also contain specific reagents performing desired functions, e.g., a development restrainer, as disclosed, for example, in US. Pat. No. 3,265,498.

The spacer or timing layer may be on the order of 0.1 to 0.7 mil. thick. Materials heretofore used for this purpose include polymers which exhibit inverse temperature-dependent permeability to alkali, e. g., as disclosed in US. Pat. No. 3,445,686. Materials previously employed for this layer include polyvinyl alcohol, cyanoethylated polyvinyl alcohol, hydroxypropyl polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyvinyl oxazolidinone, hydroxypropyl methyl cellulose, partial acetals of polyvinyl alcohol such as partial polyvinyl butyral and partial polyvinyl propional, polyvinyl amides such as polyacrylamide, etc. One preferred timing layer comprises a graft polymer of the type described in US. Pat. No. 3,575,701.

The neutralizing layer may be on the order of 0.3 to 1.5 mil. in thickness. In accordance with this invention it will be applied from an aqueous coating solution to include the acidic compound and hydrophobic adhesive, preferably contained at a coverage of less than 3,000 mgs./ft. The ratio of acid to reagent may be on the order of that heretofore mentioned.

and shown in the illustrative drawing may be prepared,

for example, by coating, in succession, on a gelatin subbed, 4 mil. opaque polyethylene terephthalate film base, the following layers:

1. a layer of cyan dye developer dispersed in gelatin and coated at a coverage of about 100 mgs./ft. of dye and about 80 mgs./ft. of gelatin;

2. a red-sensitive gelatino silver iodobromide emulsion coated at a coverage of about 140 mgs./ft. of silver and about 70 mgs./ft. of gelatin;

3. a layer of a 60-30-4-6 copolymer of butylacrylate, diacetone acrylamide, styrene and methacrylic acid and polyacrylamide coated at a coverage of about 150 mgs./ft. of the copolymer and about 5 mgs./ft. of polyacrylamide;

4. a layer of magenta dye developer dispersed in gelatin and coated at a coverage of about 100 mgs./ft. of dye and about 100 mgs./ft. of gelatin;

5. a green-sensitive gelatino silver iodobromide emulsion coated at a coverage of aboutt about 100 mgs./ft. of silver and about 50 mgs./ft. of gelatin;

6. a layer containing the copolymer referred to above in layer 3 and polyacrylamide coated at a coverage of about 100 mgs./ft. of copolymer and about 12 mgsllt. of polyacrylamide;

7. a layer of yellow dye developer dispersed in gelatin and coated at a coverage of about 70 mgs./ft. of dye and about 56 mgs./ft. of gelatin;

8. a blue-sensitive gelatino silver iodobromide emulsion layer including the auxiliary developer 4'- methylphenyl hydroquinone coated at a coverage of about 120 mgs./ft. of silver, about 60 mgs./ft. of gelatin and about 30 mgs./ft. of auxiliary developer; and

9. a layer of gelatin coated at a coverage of about 50 mgs./ft. of gelatin.

The three dye developers employed above may be the following:

I OH:

a cyan dye developer;

12 HO-CHz-CH: Q

N-SOz- N=N"H H1 nocir,-cn, l l N N 1 am 0 0 OH 1 C--CH2CH a magenta dye developer; and

OC3H1 N02 oamo- CH=N- a yellow dye developer.

Then a transparent 4 mil. polyethylene terephthalate film base may be coated, in succession, with the following illustrative layers:

1. a neutralizing layer prepared by coating from an aqueous solution in the aforementioned manner and then curing to provide a layer containing ethylene/- maleic anhydride copolymer and the amino resin reagentobtained upon curing from a urea-formaldehyde prepolymer, the ratio of acid to resin being about 10:1, the layer being coated at a coverage of about 1,250 mgs./ft. (about 1,000 mgs./ft. of acid);

2. a graft copolymer of acrylamide and diacetone acrylamide on a polyvinyl alcohol backbone in a molar ratio of 1:3.2:l at a coverage of about'700 mgs./ft. to provide a polymeric spacer or timing layer; and

3. a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of about 400 gs./ft. and including about 20 mgs./ft. of a development restrainer, 1-phenyl-5-mercaptotetrazole, to provide a polymeric image-receiving layer containing development restrainer.

The two components may then be laminated together to provide the desired integral film unit.

A rupturable container comprising an outer layer of lead foil and an inner liner or layer of polyvinyl chloride retaining an aqueous alkaline processing solution may then be fixedly mounted on the leading edge of each of the laminates, by pressure-sensitive tapes, interconnecting the respective container and laminates so that, upon application of compressive pressure to the container to rupture the containers marginal seal,

' 13 its contents may be distributed between the dyeable stratum (layer 3 of the positive component) and the gelatin layer (layer. 9) of the negative component.

An illustrative processing composition to be employed in the rupturable container may comprise the following properties of ingredients:

Waber--.- 100 cc. Potamum hydroxide 11.2 gms. Hydro ethyl cellulose (high viscosity [commercially 3.4 gms.

avall le from Hercules Powder 00., ilmington, Delawere, under the trade name Netrasol 250]. N-phenethy1-mpicolinlum bromide 2.7 gms. Benzotrlazole 1.15 gms. Titanium dioxide 50.0 gms.

H H N N l1-C His-O (B) OH OH 52 gms.

. @fic fl n "Edi." j' i 0 1.18 m.

O E Q on CHr-N- C H1511 -CH; l

This film unit may then be exposed in known manner to form a developable image and the thus exposed element may then be developed by applying compressive pressure to the rupturable container in order to distribute the aqueous alkaline processing composition, thereby forming a multicolor transfer image which is viewable through the transparent polyethylene terephthalate film base as a positive reflection print.

Apart from the advantages heretofore mentioned, while it has not as yet been conclusively established, initial findings indicate that the neutralizing layers of this invention, e.g., a film unit containing the same of the LII type shown in the foregoing illustrative example, pos sess improved stability against darkening or staining by either photolysis or heat, thereby providing improved stability against the degradative effects of light and/or heat on the quality of the resulting color print.

When the neutralizing layers of this invention are employed in association with a negative component including one or more cross-linkage layers, e.g., in the positive component of an integral negative-positive film unit including a negative component having one or more cross-linkage layers, it has been found that in some instances small amounts of aldehyde contained in the neutralizing layer tend to diffuse to this negative component under high humidity storage conditions to cause cross-linking of the aforementioned crosslinkable layer or layers which in turn may produce undesirable results in terms of the quality of the resulting print. This cross-linking may, for example, impede dye transfer to lower the density of one or more of the imaging dyes transferred to the dyeable stratum. By way of example, in the aforementioned illustrative film unit, under standard high humidity storage test conditions, e.g., 120F, percent relative humidity for 5 days, a decrease in cyan dye transfer was noted. It is believed that this is due to a diffusion during high humidity storage conditions of small amounts of formaldehyde to the interlayer between the green-sensitive emulsion and the cyan dye developer, causing some cross-linking and subsequent hardening and loss of permeability of this layer to the cyan dye developer diffusing therethrough to the dyeable stratum. It has been found that this problem may be obviated by incorporating a scavenger for this diffusing formaldehyde in the neutralizing layer, e.g., a substance which is cross-linkable by formaldehyde or any other cross-linking agent included in the neutralizing layer. The scavenger is preferably a material such as a polyhydroxy compound, e. g., polyvinyl alcohol, which can crosslink the ureaformaldehyde resin to form a more stable polymer with less tendency to release formaldehyde. It will be appreciated that the amount of such a cross-linking agent which is employed should be greater than the amount needed for this cross-linking, so that some excess of this reagent is available to scavenge any formaldehyde which may otherwise be available for diffusion. It will also be appreciated that where any problem of diffusing formaldehyde exists, excess formaldehyde should not be included in the coating composition, as mentioned previously. By way of example, it has been found that this problem may be obviated by including on the order of 10 percent by weight of the acid in this layer (e.g., mgslft. in the illustrative example) of polyvinyl alcohol. Interestingly, the addition of the polyvinyl alcohol to obviate this problem has been found to offer the further advantage of increasing the adhesion against delamination of the neutralizing layer still further at both interfaces of this layer.

Accordingly, in any film units including the neutralizing layer of this invention, where any problem exists of aldehyde present in this layer diffusing during storage to affect adversely the ability of the resulting film unit structureto function in its most favorable manner to achieve optimum image quality, it is within the scope of this invention to incorporate a scavenger for this cross-linking agent, e.g., polyvinyl alcohol, in the neutralizing layer and/or possibly in an overlying layer.

it will of course be appreciated that this is not an inherent problem in all film units contemplated by this invention and, accordingly, the use of such an additional reagent is not, generally speaking, necessary in the practice of this invention.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. ln a photographic product comprising a photosensitive element including at least one light-sensitive silver halide layer having a dye image-providing material associated therewith or an image-receiving element including a stratum adapted for receiving an .image by diffusion transfer, said photographic product including a neutralizing layer for lowering the environmental pH subsequent to application of an aqueous alkaline processing composition;

the improvement wherein said neutralizing layer comprises a hydrophilic acidic polymer and a hydrophobic adhesive reagent comprising an amino resin prepolymer which can be converted to said reagent, said neutralizing layer being applied to said photographic product from an aqueous coating solution including said acidic polymer and a water-soluble precursor for said reagent, after application of which coating solution said aqueous solvent is removed and said precursor is converted to said reagent to provide said neutralizing layer.

2. A photographic product of claim 1 wherein said prepolymer is a urea-formaldehyde condensation prepolymer.

3. A photosensitive element including at least one light-sensitive silver halide layer having a dye imageproviding material associated therewith and a neutralizing layer comprising a hydrophilic acidic polymer and a hydrophobic condensation polymer derived from an amino resin prepolymer.

4. A photosensitive element as defined in claim 3 including a dyeable stratum adapted for forming a color image by diffusion transfer.

5. A photosensitive element as defined in claim 4 wherein said dyeable stratum is disposed between said silver halide strata and associated dye image-providing material and said neutralizing layer.

6. In an integral negative-positive film unit including a negative component comprising at least one lightsensitive silver halide emulsion layer having a dye image-providing material associated therewith, a positive component including at least a dyeable stratum, said film unit further including a neutralizing layer for lowering the environmental pH subsequent to application of said alkaline processing fluid;

the improvement wherein said neutralizing layer comprises a hydrophilic acidic polymer and a hydrophobic adhesive reagent, said neutralizing layer being applied to said photographic product from an aqueous coating solution including said acidic polymer and a water-soluble precursor for said reagent which comprises an amino resin prepolymer and after application of said coating solution, said aqueous solvent is removed and said precursor is converted to said reagent to provide said neutralizing layer.

7. A film unit as defined in claim 6 wherein said neutralizing layer is disposed on the side of said dyeable stratum opposed from said negative component.

8. A film unit as defined in claim 7 wherein a timing layer is disposed between said dyeable stratum and said neutralizing layer.

9. A film unit as defined in claim 7 wherein said negative component includes a red-sensitive silver halide emulsion having a cyan dye image-providing material associated therewith, a green-sensitive silver halide emulsion having a magneta dye image-providing material associated therewith and a blue-sensitive silver halide emulsion having a yellow dye image-providing material associated therewith.

10. A film unit as defined in claim 9 wherein said dye image-providing materials are initially soluble or diffusible in said aqueous alkaline processing fluid but are selectively rendered non-diffusible in an imagewise pattern as a function of development.

11. A film unit as defined in claim 6 wherein said negative and positive components are confined between a pair of support members, at least the support member associated with the positive component being transparent.

12. A film unit as defined in claim 6 wherein said positive and negative components are confined on a transparent support member associated with said positive component.

13. A film unit as defined in claim 6, including a layer of a white pigment disposed in a layer between said positive and negative components.

14. A film unit of claim 6 wherein said prepolymer is a urea-formaldehyde condensation prepolymer.

15. A film unit as defined in claim 14 wherein said polymer is an amino resin and said acidic polymer is a polymeric acid.

16. Aphotosensitive element including a composite structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer, a layer containing a cyan dye developer, a red-sensitive gelatino silver halide emulsion layer, a layer containing a magenta dye developer, a greensensitive gelatino silver halide emulsion layer, a layer containing a yellow dye developer, a blue-sensitive gelatino silver halide emulsion layer, a dyeable stratum, a neutralizing layer comprising a hydrophilic polymeric acid in an amount sufficient to effect reduction of a processing solution having a first pH at which said dye developers are soluble and diffusible to a second pH at which said dye developers are substantially insoluble and non-diffusible, said neutralizing layer further including a hydrophobic condensation polymer derived from an amino resin prepolymer, the ratio of said acid to said polymer in said neutralizing layer being from about 5:1 to about 20:1, a dimensionally stable alkaline solution impermeable transparent layer, means securing at least the side edges of said opposed layer in fixed relationship, and a rupturable container retaining an aqueous alkaline processing solution having said first pH and containing dispersed therein a white inorganic pigment in a quantity sufficient to mask effectively said silver halide layers and any dye developer associated therewith after development and to provide a background for viewing a diffusion transfer image formed by development of said film unit, by reflected light, through said transparent layer, said rupturable container being fixedly positioned and extending transverse a leading edge of said photosensitive element so as to be capable of effecting unidirectional discharge of the containers contents between said dyeable stratum and said blue-sensitive emuslion'layer upon application of compressive force to said container.

17. A photosensitive element as defined in claim 16 wherein said polymer is a urea-formaldehyde condensation polymer.

18. A film unit as defined in claim 17 wherein said polymeric acid is a ethylene/maleic anhydride copolymer.

19. A film unit as defined in claim 16 wherein said cyan dye developer is a phthalocyanine dye developer; said magenta dye developer is a 1:1 chrome-complexed azo dye developer; and said yellow dye developer is a 1:1 chrome-complexed azomethine dye developer.

20. A film unit as defined in claim 19 including a timing layer disposed between said dyeable stratum and said neutralizing layer.

21. A process for forming a visible image in color 18 comprising the steps of exposing a photosensitive element as defined in claim 4 to form a developable image and thereafter applying an aqueous alkaline processing composition to said exposed element to form said color image.

22. A process for forming a color transfer image comprising the steps of exposing a film unit as defined in claim 6 to form a developable image and thereafter applying an aqueous alkaline processing composition to develop said image and to form, as a function of development, an imagewise distribution of dye imageproviding material which is transferred, at least in part, by diffusion, to said dyeable stratum to impart thereto a color transfer image viewable, without separation, by reflected light as a positive color reflection print.

23. A film unit as defined in claim 16 including an aqueous alkaline processing fluid having a white pig- 

2. A photographic product of claim 1 wherein said prepolymer is a urea-formaldehyde condensation prepolymer.
 3. A photosensitive element including at least one light-sensitive silver halide layer having a dye image-providing material associated therewith and a neutralizing layer comprising a hydrophilic acidic polymer and a hydrophobic condensation polymer derived from an amino resin prepolymer.
 4. A photosensitive element as defined in claim 3 including a dyeable stratum adapted for forming a color image by diffusion transfer.
 5. A photosensitive element as defined in claim 4 wherein said dyeable stratum is disposed between said silver halide strata and associated dye image-providing material and said neutralizing layer.
 6. In an integral negative-positive film unit including a negative component comprising at least one light-sensitive silver halide emulsion layer having a dye image-providing material associated therewith, a positive component including at least a dyeable stratum, said film unit further including a neUtralizing layer for lowering the environmental pH subsequent to application of said alkaline processing fluid; the improvement wherein said neutralizing layer comprises a hydrophilic acidic polymer and a hydrophobic adhesive reagent, said neutralizing layer being applied to said photographic product from an aqueous coating solution including said acidic polymer and a water-soluble precursor for said reagent which comprises an amino resin prepolymer and after application of said coating solution, said aqueous solvent is removed and said precursor is converted to said reagent to provide said neutralizing layer.
 7. A film unit as defined in claim 6 wherein said neutralizing layer is disposed on the side of said dyeable stratum opposed from said negative component.
 8. A film unit as defined in claim 7 wherein a timing layer is disposed between said dyeable stratum and said neutralizing layer.
 9. A film unit as defined in claim 7 wherein said negative component includes a red-sensitive silver halide emulsion having a cyan dye image-providing material associated therewith, a green-sensitive silver halide emulsion having a magneta dye image-providing material associated therewith and a blue-sensitive silver halide emulsion having a yellow dye image-providing material associated therewith.
 10. A film unit as defined in claim 9 wherein said dye image-providing materials are initially soluble or diffusible in said aqueous alkaline processing fluid but are selectively rendered non-diffusible in an imagewise pattern as a function of development.
 11. A film unit as defined in claim 6 wherein said negative and positive components are confined between a pair of support members, at least the support member associated with the positive component being transparent.
 12. A film unit as defined in claim 6 wherein said positive and negative components are confined on a transparent support member associated with said positive component.
 13. A film unit as defined in claim 6, including a layer of a white pigment disposed in a layer between said positive and negative components.
 14. A film unit of claim 6 wherein said prepolymer is a urea-formaldehyde condensation prepolymer.
 15. A film unit as defined in claim 14 wherein said polymer is an amino resin and said acidic polymer is a polymeric acid.
 16. A photosensitive element including a composite structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer, a layer containing a cyan dye developer, a red-sensitive gelatino silver halide emulsion layer, a layer containing a magenta dye developer, a green-sensitive gelatino silver halide emulsion layer, a layer containing a yellow dye developer, a blue-sensitive gelatino silver halide emulsion layer, a dyeable stratum, a neutralizing layer comprising a hydrophilic polymeric acid in an amount sufficient to effect reduction of a processing solution having a first pH at which said dye developers are soluble and diffusible to a second pH at which said dye developers are substantially insoluble and non-diffusible, said neutralizing layer further including a hydrophobic condensation polymer derived from an amino resin prepolymer, the ratio of said acid to said polymer in said neutralizing layer being from about 5:1 to about 20:1, a dimensionally stable alkaline solution impermeable transparent layer, means securing at least the side edges of said opposed layer in fixed relationship, and a rupturable container retaining an aqueous alkaline processing solution having said first pH and containing dispersed therein a white inorganic pigment in a quantity sufficient to mask effectively said silver halide layers and any dye developer associated therewith after development and to provide a background for viewing a diffusion transfer image formed by development of said film unit, by reflected light, through said transparent layer, said rupturable container being fixedly positioned and extending transverse a leading edge of said photosensitive element so as to be capable of effecting unidirectional discharge of the container''s contents between said dyeable stratum and said blue-sensitive emuslion layer upon application of compressive force to said container.
 17. A photosensitive element as defined in claim 16 wherein said polymer is a urea-formaldehyde condensation polymer.
 18. A film unit as defined in claim 17 wherein said polymeric acid is a ethylene/maleic anhydride copolymer.
 19. A film unit as defined in claim 16 wherein said cyan dye developer is a phthalocyanine dye developer; said magenta dye developer is a 1:1 chrome-complexed azo dye developer; and said yellow dye developer is a 1:1 chrome-complexed azomethine dye developer.
 20. A film unit as defined in claim 19 including a timing layer disposed between said dyeable stratum and said neutralizing layer.
 21. A process for forming a visible image in color comprising the steps of exposing a photosensitive element as defined in claim 4 to form a developable image and thereafter applying an aqueous alkaline processing composition to said exposed element to form said color image.
 22. A process for forming a color transfer image comprising the steps of exposing a film unit as defined in claim 6 to form a developable image and thereafter applying an aqueous alkaline processing composition to develop said image and to form, as a function of development, an imagewise distribution of dye image-providing material which is transferred, at least in part, by diffusion, to said dyeable stratum to impart thereto a color transfer image viewable, without separation, by reflected light as a positive color reflection print.
 23. A film unit as defined in claim 16 including an aqueous alkaline processing fluid having a white pigment dispersed therein. 